CHEK2 and breast cancer: Some of the most frequent gene mutations that predispose an increased risk of breast cancer include ataxia-telangiectasia mutated (ATM), BRCA1-associated RING domain 1 (BARD1), BReast CAncer gene 1 (BRCA1), BReast CAncer gene 2 (BRCA2), cadherin 1 (CDH1), checkpoint kinase 2 (CHEK2), neurofibromatosis type 1 (NF1), partner and localizer of BRCA2 (PALB2), phosphatase and tensin homolog deleted on chromosome 10 (PTEN), serine/threonine kinase 11 (STK11), and tumor protein 53 (TP53) [8,9]; however, the most common high-penetrance susceptibility alleles remain BRCA1 and BRCA2 [2].